1. Field of the Invention
This invention relates generally to the dispersion of polymers into water and, more particularly, this invention relates to a method and apparatus for rapidly dispersing dry, water soluble polymer particles into water.
2. Description of the Prior Art
The use of solutions of water soluble polymers in thickening and flocculating applications is well known. Such applications include the clarification of aqueous solutions in papermaking, and in treatment of sewage and industrial wastes. Such solutions of polymers are also useful as stabilizers for drilling muds, and in the secondary recovery of petroleum by water flooding.
Although these polymers are most often available commercially as powders or as finely divided solids, they are most frequently utilized in aqueous solutions. This necessitates that the solid polymer material be dissolved in water. Although the various polymers are more or less soluble in water, difficulty is often experienced in preparing aqueous polymer solutions because of their slow dissolution and because the solid polymer is not readily dispersible in water.
Furthermore, dispersion of solid polymers in water is hindered by the tendency of polymer particles to clump or remain as agglomerates on contact with water. Lumps of solid polymer immediately form after limited wetting with water by the encapsulation of undissolved solids in an outer coating of water-wet polymer which retards the penetration of additional water into the agglomerate. Although many of these lumps are eventually dissolved by continued agitation, it is frequently impractical to agitate the solution for a sufficiently long period to obtain complete dissolution. Long mixing times, of course, are uneconomical and may damage polymer molecular weight through exposure of the polymer to excessive hydraulic and mechanical shear.
The problem is compounded by the fact that dry polymer particles usually include very fine, dustlike particles. This creates pollution problems in the vicinity of the equipment and can aggravate the problem of buildup of sticky or slippery polymer on equipment surfaces.
The foregoing problems are described in numerous prior publications, including U.S. Pat. Nos. Re. 28,474 (July 8, 1974) and Re. 28,576 (Oct. 21, 1975) issued to Anderson et al.
The above-identified Anderson et al reissue patents exemplify prior approaches to overcoming the problem of rapidly dissolving polymers in the water. In the Anderson et al disclosures, water soluble polymer is dispersed into a water-in-oil emulsion, which emulsion is then inverted in water to release the polymer into solution.
The method of the Anderson et al disclosures is limited in terms of the polymer content of the emulsion. Further, such systems, in practice, require substantial amounts of an emulsifier to provide a stable product and, of course, require the use of an oil phase, which creates handling and economic problems.